JBoss Portal will not run on AS4.0.2 as that version of AS uses Hibernate3. We recommend 4.0.1sp1, as we mainly develop on that version containing Hibernate2. We hope to have it running on 4.0.2 for our Final in June.
I will modify the docs and make it clearer that we do not support 4.0.2 currently. http://docs.jboss.org/jbportal/v2.0RC/user-guide/en/html/supportedversions.html#d0e355
Let me know if this helped.